Make Discord id length variable and fix webhook hash (#16)

* prevent duplicate user for interactions

* fix for older discord accounts

* check channel mentions against full channel list

* Fix compatibility for Python 3.7

Replace dict with Dict object from typing module

* remove scary hashing

* always expect guild_id

* change hash to djb2

* Revert "always expect guild_id"

This reverts commit dbcb3d1b9c97f6ceda0cf982b4bd7228926112c3.

* guild_id warning, don't group bot created webhooks

* fmt

Co-authored-by: Friskygote <7283122+Friskygote@users.noreply.github.com>
Co-authored-by: Wolf Gupta <e817509a-8ee9-4332-b0ad-3a6bdf9ab63f@aleeas.com>

appservice/discord.py

@@ -3,7 +3,6 @@ from dataclasses import dataclass
 from misc import dict_cls
 
 CDN_URL = "https://cdn.discordapp.com"
-ID_LEN = 18
 MESSAGE_LIMIT = 2000
 
 
@@ -107,6 +106,9 @@ class Message:
         self.channel_id = message["channel_id"]
         self.content = message.get("content", "")
         self.id = message["id"]
+        self.guild_id = message.get(
+            "guild_id", ""
+        )  # Responses for sending webhook messages don't have guild_id
         self.webhook_id = message.get("webhook_id", "")
         self.application_id = message.get("application_id", "")
 

appservice/gateway.py

@@ -2,7 +2,7 @@ import asyncio
 import json
 import logging
 import urllib.parse
-from typing import List
+from typing import Dict, List
 
 import urllib3
 import websockets
@@ -148,6 +148,18 @@ class Gateway:
 
         return dict_cls(resp, discord.Channel)
 
+    def get_channels(self, guild_id: str) -> Dict[str, discord.Channel]:
+        """
+        Get all channels for a given guild ID.
+        """
+
+        resp = self.send("GET", f"/guilds/{guild_id}/channels")
+
+        return {
+            channel["id"]: dict_cls(channel, discord.Channel)
+            for channel in resp
+        }
+
     def get_emotes(self, guild_id: str) -> List[discord.Emote]:
         """
         Get all the emotes for a given guild.

appservice/main.py

@@ -5,11 +5,11 @@ import os
 import re
 import sys
 import threading
+import urllib.parse
 from typing import Dict, List, Tuple
 
 import markdown
 import urllib3
-import urllib.parse
 
 import discord
 import matrix
@@ -28,7 +28,7 @@ class MatrixClient(AppService):
         self.db = DataBase(config["database"])
         self.discord = DiscordClient(self, config, http)
         self.format = "_discord_"  # "{@,#}_discord_1234:localhost"
-        self.id_regex = f"[0-9]{{{discord.ID_LEN}}}"
+        self.id_regex = "[0-9]+"  # Snowflakes may have variable length
 
         # TODO Find a cleaner way to use these keys.
         for k in ("m_emotes", "m_members", "m_messages"):
@@ -329,28 +329,40 @@ height=\"32\" src=\"{emote_}\" data-mx-emoticon />""",
 
         return message
 
-    def mention_regex(self, encode: bool) -> str:
+    def mention_regex(self, encode: bool, id_as_group: bool) -> str:
         mention = "@"
         colon = ":"
+        snowflake = self.id_regex
 
         if encode:
             mention = urllib.parse.quote(mention)
             colon = urllib.parse.quote(colon)
 
-        return f"{mention}{self.format}{self.id_regex}{colon}{re.escape(self.server_name)}"
+        if id_as_group:
+            snowflake = f"({snowflake})"
+
+        hashed = f"(?:-{snowflake})?"
+
+        return f"{mention}{self.format}{snowflake}{hashed}{colon}{re.escape(self.server_name)}"
 
     def process_message(self, event: matrix.Event) -> str:
         message = event.new_body if event.new_body else event.body
 
         emotes = re.findall(r":(\w*):", message)
 
-        mentions = re.findall(
+        mentions = list(
-            self.mention_regex(encode=False), event.formatted_body
+            re.finditer(
+                self.mention_regex(encode=False, id_as_group=True),
+                event.formatted_body,
+            )
         )
         # For clients that properly encode mentions.
         # 'https://matrix.to/#/%40_discord_...%3Adomain.tld'
         mentions.extend(
-            re.findall(self.mention_regex(encode=True), event.formatted_body)
+            re.finditer(
+                self.mention_regex(encode=True, id_as_group=True),
+                event.formatted_body,
+            )
         )
 
         with Cache.lock:
@@ -361,19 +373,20 @@ height=\"32\" src=\"{emote_}\" data-mx-emoticon />""",
 
         for mention in set(mentions):
             # Unquote just in-case we matched an encoded username.
-            username = self.db.fetch_user(urllib.parse.unquote(mention)).get(
+            username = self.db.fetch_user(
-                "username"
+                urllib.parse.unquote(mention.group(0))
-            )
+            ).get("username")
             if username:
-                match = re.search(self.id_regex, mention)
+                if mention.group(2):
-
+                    # Replace mention with plain text for hashed users (webhooks)
-                if match:
+                    message = message.replace(mention.group(0), f"@{username}")
+                else:
                     # Replace the 'mention' so that the user is tagged
                     # in the case of replies aswell.
                     # '> <@_discord_1234:localhost> Message'
-                    for replace in (mention, username):
+                    for replace in (mention.group(0), username):
                         message = message.replace(
-                            replace, f"<@{match.group()}>"
+                            replace, f"<@{mention.group(1)}>"
                         )
 
         # We trim the message later as emotes take up extra characters too.
@@ -456,9 +469,10 @@ class DiscordClient(Gateway):
             or message.webhook_id in hook_ids
         )
 
-    def matrixify(self, id: str, user: bool = False) -> str:
+    def matrixify(self, id: str, user: bool = False, hashed: str = "") -> str:
         return (
-            f"{'@' if user else '#'}{self.app.format}{id}:"
+            f"{'@' if user else '#'}{self.app.format}"
+            f"{id}{'-' + hashed if hashed else ''}:"
             f"{self.app.server_name}"
         )
 
@@ -490,11 +504,11 @@ class DiscordClient(Gateway):
         Discord user.
         """
 
-        if message.webhook_id and not message.application_id:
+        hashed = ""
-            hashed = hash_str(message.author.username)
+        if message.webhook_id and message.webhook_id != message.application_id:
-            message.author.id = str(int(message.author.id) + hashed)
+            hashed = str(hash_str(message.author.username))
 
-        mxid = self.matrixify(message.author.id, user=True)
+        mxid = self.matrixify(message.author.id, user=True, hashed=hashed)
         room_id = self.app.get_room_id(self.matrixify(message.channel_id))
 
         if not self.app.db.fetch_user(mxid):
@@ -666,14 +680,23 @@ class DiscordClient(Gateway):
                     f"<@{char}{member.id}>", f"@{member.username}"
                 )
 
-        # `except_deleted` for invalid channels.
+        # Replace channel IDs with names.
-        # TODO can this block for too long ?
+        channels = re.findall("<#([0-9]+)>", content)
-        for channel in re.findall(f"<#([0-9]{{{discord.ID_LEN}}})>", content):
+        if channels:
-            discord_channel = except_deleted(self.get_channel)(channel)
+            if not message.guild_id:
-            name = (
+                self.logger.warning(
-                discord_channel.name if discord_channel else "deleted-channel"
+                    f"Message '{message.id}' in channel '{message.channel_id}' does not have a guild_id!"
-            )
+                )
-            content = content.replace(f"<#{channel}>", f"#{name}")
+            else:
+                discord_channels = self.get_channels(message.guild_id)
+                for channel in channels:
+                    discord_channel = discord_channels.get(channel)
+                    name = (
+                        discord_channel.name
+                        if discord_channel
+                        else "deleted-channel"
+                    )
+                    content = content.replace(f"<#{channel}>", f"#{name}")
 
         # { "emote_name": "emote_id" }
         for emote in re.findall(regex, content):

appservice/misc.py

@@ -73,13 +73,12 @@ def except_deleted(fn):
 
 def hash_str(string: str) -> int:
     """
-    Create the hash for a string (poorly).
+    Create the hash for a string
     """
 
-    hashed = 0
+    hash = 5381
-    results = map(ord, string)
 
-    for result in results:
+    for ch in string:
-        hashed += result
+        hash = ((hash << 5) + hash) + ord(ch)
 
-    return hashed
+    return hash & 0xFFFFFFFF